The Study On Resistance To Pests Of The Transgenic Bt Rice

The resistance to yellow stem borer (YSB)and influences on main pests and natural enemies in rice field were studied using the transgenic indica rice CMS restorer line Minghui63(T51-l) and its derived varieties, II you/Bt,Shangyou63/Bt, Mayou/Bt, expressing a Bt fusion protein derived from crylA(b) and crylA(c) sequences, Shangyou63 and Minghui63 as the control varieties.Using the two methods of "detached leaf bioassay" and "detached stem bioassay", both of the laboratory bioassay showed that T51-1 was highly resistant to the newly hatched YSB with the moralities of 100% after 72h, the laboratory bioassay results of the two methods were quite coincident with those of the whole plant manual infestation in rice field. The resistance of transgenic Bt rice to YSB varied with the rice structures and its developmental stages. The resistance of Bt rice in leaf to YSB was lower.than that of the stem; on the other hand, the resistance of Bt rice at spike formation stage to YSB was higher than that at tree-leaved stage. With the difference of instar, the resistance of Bt rice to the YSB was also different. The 3rd instar larvae was more resistant to Bt rice than the 1st instar larvae.The transgenic Bt rice(T51-1) looked as a criterion, forty different normal rice varieties were carried out to select the resistant varieties to the main different pests ,such as the YSB, leaffolder ,and rice planthopper( including the White-backed planthopper and the Brown planthopper).Systematic studies were carried out on effects of transgenic Bt rice on population dynamic of the main pest and their natural enemies in rice field .The result showed that transgenic Bt rice was highly resistant to YSB,leaffolder; but it was not that resistant to the rice planthopper, on the contrary, there were more rice planthoppers in Bt rice than in normal rice varieties. Luckily, there were not any significant difference of the number of spiders on transgenic Bt rice than on normal rice in the field, it was assessed that there were no harm to spiders in transgenic Bt rice field.The transgenic Bt rice was very resistant to the main Lepidopterous pests, such as the YSB and leaffolder ,It was not obviously easy to find the two kind pests in transgenic Bt rice field. But the rice planthopper was easy to break heavily in transgenic rice field .We used the index of the enemy function to assess the natural enemy -spiders' control action to the rice planthopper, The result showed that the spiders' control action was very obvious when the number of the rice planthopper was under the control threshhold , otherwise, we should take action immediately to decrease the number of the rice planthopper, using the agriculture insecticide-Bichonglin ,which was very effective to control the rice planthopper and do little harm to the spiders.